Inkjet-printed graphene electrodes for dye-sensitized solar cells

We present a stable inkjet printable graphene ink, formulated in isopropyl alcohol via liquid phase exfoliation of chemically pristine graphite with a polymer stabilizer. The rheology and low deposition temperature of the ink allow uniform printing. We use the graphene ink to fabricate counter electrodes (CE) for natural and ruthenium-based dye-sensitized solar cells (DSSCs). The repeatability of the printing process for the CEs is demonstrated through an array of inkjet-printed graphene electrodes, with ∼5% standard deviation in the sheet resistance. As photosensitizers, we investigate natural tropical dye extracts from Pennisetum glaucum, Hibiscus sabdariffa and Caesalpinia pulcherrima. Among the three natural dyes, we find extracts from C. pulcherrima exhibit the best performance, with ∼0.9% conversion efficiency using a printed graphene CE and a comparable ∼1.1% efficiency using a platinum (Pt) CE. When used with N719 dye, the inkjet-printed graphene CE shows a ∼3.0% conversion efficiency, compared to ∼4.4% obtained using Pt CEs. Our results show that inkjet printable graphene inks, without any chemical functionalization, offers a flexible and scalable fabrication route, with a material cost of only ∼2.7% of the equivalent solution processed Pt-based electrodes.Authors acknowledge support from CAPREX, Cambridge Africa Alborada Fund, Carnegie-University of Ghana Next Generation of Africa Academics programme and the Royal Academy of Engineering (RAEng) through a research fellowship (Graphlex)

The influence Of Bi2O3 and Sb2O3 doping on the microstructure and electrical properties of sintered zinc oxide

The influence of Bi2O3 and Sb2O3 doping on the microstructure and electrical characteristics of Zinc Oxide based varistor has been investigated. The as-sintered ceramic varistors with different compositions have been characterized via laboratory X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and electrical measurements. Bismuth oxide doping resulted in liquid phase sintering, rapid densification, grain growth and electrical varistor precipitating to a spinel phase and thereby inhibiting grain growth. Electrical property measurements indicate varistor behaviour for both cases of doping.http://www.arpnjournals.com/jeas/index.ht

Microemulsion synthesis of copper oxide nanorod-like structures

Copper oxide (CuO) nanorod-like structures made of spherical nanocrystals were synthesized at moderate temperature (80◦C) starting from CuCl2·2H2O crystals in a water/n-heptane microemulsion stabilised by the nonionic Brij-30 surfactant. Whole Powder Pattern Modelling of the X-ray diffraction pattern shows absence of linear and planar defects with crystalline domains in the range of 4–8 nm. A linear correlation between the average size of the particles and the quantity of water in the system was observed: all synthesised specimens show a large blue shift of the energy bandgap (up to 2.7 eV versus 1.2 eV of bulk CuO) resulting from quantum confinement effects. The mechanism of growth of the spherical nanoparticles into nanorod-like structures has been elucidated.http://www.tandfonline.com/loi/gmcl2

H2O2 rejuvenation-mediated synthesis of stable mixed-morphology Ag3PO4 photocatalysts.

Ag3PO4 photocatalyst has attracted interest of the scientific community in recent times due to its reported high efficiency for water oxidation and dye degradation. However, Ag3PO4 photo-corrodes if electron accepter such as AgNO3 is not used as scavenger. Synthesis of efficient Ag3PO4 followed by a simple protocol for regeneration of the photocatalyst is therefore a prerequisite for practical application. Herein, we present a facile method for the synthesis of a highly efficient Ag3PO4, whose photocatalytic efficiency was demonstrated using 3 different organic dyes: Methylene Blue (MB), Methyl orange (MO) and Rhodamine B (RhB) organic dyes for degradation tests. Approximately, 19 % of Ag3PO4 is converted to Ag0 after 4.30 hours of continuous UV-Vis irradiation in presence of MB organic dye. We have shown that the Ag/Ag3PO4 composite can be rejuvenated by a simple chemical oxidation step after several cycles of photocatalysis tests. At an optimal pH of 6.5, a mixture of cubic, rhombic dodecahedron, nanosphere and nanocrystals morphologies of the photocatalyst was formed. H2O2 served as the chemical oxidant to re-insert the surface metallic Ag into the Ag3PO4 photocatalyst but also as the agent that can control morphology of the regenerated as-prepared photocatalyst without the need for any other morphology controlling Agent (MCA). Surprisingly, the as- regenerated Ag3PO4 was found to have higher photocatalytic reactivity than the freshly made material and superior at least 17 times in comparison with the conventional Degussa TiO2, and some of TiO2 composites tested in this work

Assessment of fluoride removal in a batch electrocoagulation process: A case study in the Mount Meru Enclave

This research article published by Elsevier B.V., 2021The presence of excessive amounts of fluoride than prescribed standards has been reported in various sources of domestic water supply around the slopes of Mount Meru and other parts in Tanzania. Efforts to remove the excessive fluoride have been carried out using various technologies. In this study, electrocoagulation experiments were carried out to assess its efficiency on fluoride removal. The fluoride concentration tested ranged from 1.37 to 48 mg/L in both synthetic and natural waters. The voltage applied in the electrocoagulation (EC) process ranged from 0 to 50 V while maintaining pH values of 4 to 9. The representative experimental results for the Ngarenanyuki river water with initial fluoride concentration of 29.5 mg/L accomplished a removal efficiency of 90% at an optimal electrolysis time of 30 min, an applied voltage of 30 V and an optimal pH of 6. The method showed efficient fluoride removal in water to allowable limits by World Health Organization (WHO) and Tanzania Bureau of Standards (TBS) (1.5 mg/L). Despite the voltage applied (30 V), the pH at neutrality remained unchanged thus making the process more efficient. At this voltage (30 V) the process has been reported previously also to have the capability of disinfecting the water and hence rendering such water safe for us

DNA hybridisation sensors for product authentication and tracing : state of the art and challenges

Abstract: The wide use of biotechnology applications in bioprocesses such as the food and beverages industry, pharmaceuticals, and medical diagnostics has led to not only the invention of innovative products but also resulted in consumer and environmental concerns over the safety of biotechnology-derived products. Controlling and monitoring the quality and reliability of biotechnology-derived products is a challenge. Current tracking and tracing systems such as barcode labels and radio frequency identification systems track the location of products from primary manufactures and/or producers throughout globalised distribution channels. However, when it comes to product authentication and tracing, simply knowing the location of the product in the supply chain is not sufficient. DNA hybridisation sensors allows for a holistic approach into product authentication and tracing in that they enable the attribution of active ingredients in biotechnology-derived products to their source. In this article, the state-of-the-art of DNA hybridisation sensors, with a focus on the application of graphene as the backbone, for product authentication and tracing is reviewed. Candidate DNA biocompatible materials, properties and transduction schemes that enable detection of DNA are covered in the discussion. Limitations and challenges of the use of DNA biosensing technologies in real-life environmental, biomedical and industrial fields as opposed to clean-cut laboratory conditions are also enumerated. By considering experimental research versus reality, this article outlines and highlights research needed to overcome commercialisation barriers faced by DNA biosensing technologies. In addition, the content is thought-provoking to facilitate development of cutting edge research activities in the field

Dynamic Mechanical Behaviour of Coir and Coconut Husk Particulate Reinforced Polymer Composites: The Effect of Exposure to Acidic Environment

This chapter describes an experimental investigation into the dynamic mechanical properties of coir and coconut husk particulate reinforced polymer composites which were prepared by the hot press method. The composite was immersed in a strongly acidic environment of pH 2.2 for a period of 14 and 28 days (14P and 28P). Values of storage modulus at different vibrational frequencies recorded for the polymers at low temperatures where the molecules are still tightly compressed and the region of first solid state transitions are: Control sample (CS)—913.18, 984.18 and 979.94 MPa; 14P—505.54, 492.47 and 473.60 MPa and 28P—282.25, 298.70 and 285.36 MPa at 2, 5 and 10 Hz, respectively. While values of loss modulus at different vibrational frequencies are: CS—113.32, 109.43 and 107.62 MPa, 14P—92.92, 92.92 and 101.93 MPa and 28P—46.08, 45.61 and 45.18 MPa at 2, 5 and 10 Hz, respectively. Degradation of the mechanical properties was ascribed to the penetration and absorption that occurred between the acid solution and the composite constituents (matrix, filler, and fiber). It was found that frequency variation influenced the dynamic mechanical properties of the polymer composite at the points of measurement

Managing non-revenue water in Mwanza, Tanzania: A fast-growing sub-Saharan African city

This research articles was published in Journals Scientific African Volume 12,2021,High non-revenue water (NRW) and unreliable water supply services are major challenges in operations of the water infrastructure of most fast-growing cities in developing coun- tries. In this study, an analysis of the existing distribution network was carried out to investigate its performance concerning water loss reduction and system improvement. A high percentage of NRW (50%) was found in a selected district metering area (DMA) com- pared to the city’s entire network (37%). About 87% of the NRW was contributed by real losses in the DMA, while about 52% of the nodal junctions had pressure above the recom- mended thresholds. The high pressure was responsible for the observed leakages and pipe bursts in the DMA. Optimization of pressure by using pressure-reducing valves as well as changing the network topology minimized the potential leakages to 46%. Also, flow veloci- ties in about 83% of the pipes were found inadequate leading to poor water quality due to water stagnation. Low velocities were due to oversized indicating incidence of unplanned spatial and temporal expansion of the distribution network. This study, therefore, revealed that a comprehensive zone by zone assessment of water distribution network can improve the management of non-revenue in unplanned urban areas which is in line with ensuring the availability and sustainable management of water and sanitation for all

Surfactant assisted synthesis of copper oxide (CuO) leaf-like nanostructures for electrochemical applications

Three different copper oxide (CuO) leaf-like nanostructures have been synthesised by micelles micro emulsion method using a surfactant of copper dodecyl sulphate (Cu(DS)2) by varying the concentration of sodium hydroxide (NaOH). This study was carried out to investigate the effect of NaOH concentration on the stability, crystalline domain and pseudocapacitance behaviour of the leaf-like nanostructures. The samples were characterized by X-ray diffraction (XRD), thermogravimetry analysis (TGA), Raman spectroscopy, Fourier-Transform Infrared (FTIR), scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). It was observed that the crystalline domain size (12 nm-18 nm) and size distribution of the as-synthesized nanocrystals decreases with increasing concentration of NaOH. The interactions mechanism and formation of the leaf-like structure have been elucidated and correlated with various analytical techniques. The domain size and NaOH concentration tend to influence the charge transfer resistance.South African Research Chairs Initiative of the Department of Science and Technology (DST) and the National Research Foundation (NRF). University of Pretoria and NRF.http://journal.sapub.org/materialshb201

Silver nanoparticles decorated on a three-dimensional graphene scaffold for electrochemical applications

Silver metal nanoparticles were decorated by electron beam evaporation on graphene foam (GF) grown by chemical vapour deposition. X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, and atomic force microscopy were used to investigate the structure and morphology of the graphene foam/silver nanoparticles (GF/Ag). Both samples were tested as electrodes for supercapacitors. The GF/Ag exhibited a significantly higher capacitive performance, including a specific capacitance value of (~110 Fg-1) and excellent cyclability in a three-electrode electrochemical cell. These results demonstrate that graphene foam could be an excellent platform for metal particles for investigating improved electrochemical performance.The South African Research Chairs Initiative (SARCHi) of the Department of Science and Technology (DST) and the National Research Foundation (NRF).http://www.elsevier.com/locate/jpcshb2013ai201